Geochemical and geophysical characterization of an active CO2 gas vent near the village of Latera, Central Italy

A series of highly detailed soil gas sampling surveys have been conducted radially around various gas vents located within the Latera test site. Data indicate that active gas release occurs from a number of relatively small points on surface, implying that gas flow at depth is likely channeled along irregular gas-permeable pathways within a fault zone. To better interpret the results of these radial surveys a highly detailed horizontal profile of soil gas samples is performed across a number of the vents. If one assumes that majority of the measured trace gases all come from depth and that they are transported to surface via the high-volume advection of the thermo-metamorphically produced CO2, then, two important conclusions can be reached in regards CO2 sequestration applications. First, although it is foreseen that only CO2 is injected into a geological reservoir at depth, it must be remembered that if there is an eventual leak to surface the CO2 is likely transport other trace gases with it. Second, the different distribution of the various gas species in the shallow soil environment indicates the importance of this horizon to act as a buffer against the transfer of reduced gas species to the atmosphere. The efficiency of this buffer depends on the characteristics of the zone itself, such as unsaturated zone thickness, mineralogy, and gas permeability, as well as on the characteristics of the vent, such as flux rates and gas composition. © 2005 Elsevier Ltd. All rights reserved.